This sounds like homework. Designing a DB is a lot of work and you should go step by step with the design. You have a good example with the AdventureWorks databases, but you shouldn't copy it as it is (anyone with SQL Server experience would notice).Try to keep it simple, identify entities and their attributes and relationships. Everything comes from there.

Luis C.General Disclaimer:Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?

I think your class should have given you some idea of where to begin to build a database and how extensive they want it. Start to think about all the entities (products, cars, ..) involved, draw out the relationships between them (one to many, ... ) and the transactions that occur involving these. This is not a quick to do and you need to participate in your class through office hours or study groups to get better help.